I recently got to level 15, and went to a new zone (Ascalon I believe it was called) And the mobs/machines there to so long to kill, I invited a guild friend and basically the game got 10x more enjoyable with a partner.
It seems like solo levellers (Like I do generally, yeah yeah I know, its an mmo for a reason!) are going to have there work cut out for them. It is not even that it is a lot harder or anything, just tedious and time consuming alone!
hehe I wonder if it is player count in the area, or just in that quest area, or in the entire zone. There were some level 14-16 "End mobs" of long questlines that took literally 10 minutes to kill with ~eight players, it was just rough. If he hit you once, you died, no matter what. 4500+ damage on decent gear, with 1800 health :P
I hope the HP of the "bosses" is just because of the massive amount of people around, it is just tedious dps'ing the same thing that does the same thing for that long straight lol!